An automotive vehicle typically includes a head restraint for each of the front seats. These head restraints generally extend vertically from the seat back and may prevent neck hyperextension during rear collision as a head restraint of an automotive seat limits rearward movement of a head of an occupant. During a rear impact event, the occupant's torso is pressed into the seat due to differences in velocity between the seat and the occupant and the head of the occupant contacts the head restraint after some delay.
Many systems have been proposed for moving the head restraint forward toward the seat occupant's head in reaction to a forward acceleration of the vehicle during rear impact. Such mechanical systems that do not contain any electrical components connected to a crash sensor are referred to herein as “reactive head restraint systems.” Head restraint systems connected to a crash sensor are referred to as “active head restraint systems.” Active head restraint systems are typically more expensive than reactive systems, require resetting by a skilled automotive technician and cause discomfort to the occupant until they are reset.
Efforts have been made to provide reactive head restraints in existing seat designs equipped with passive two-way or four-way head restraint system. However, in such situations the implementation has required the provision of a new upper cross-member, which in turn requires an expensive and time-consuming revision of the seat back frame. This difficulty arises when efforts are made to package the guide sleeves of the head restraint tubes at a location within the upper cross-member of the seat back frame. To make such a change the holes in the upper cross member would have to be elongated, which in turn would require tooling revisions at the assembly line and the upper cross member for the reactive head restraint would have to be different from the one used with a passive head restraint system. The manufacturing production of multiple types of seat back frames is more expensive than for a common frame.